Reforming of naphtha



Dec. 27, 1938.

E. J. HOUDRY REFORMING OF NAPHTHA Filed April 27, 1955 Patented Dee. 27,1938 UNITED STATES PATENT OFFICE Houdry Process C poration of Delawareorporation, Dover,

i., a cor- Applioation April 27, 1935, Serial N0. 18,600

6 Claims '(Cl. 196-52) This invention relates to the treatment ofhydrocarbon distillates of mineral oil and the like at the upper end ofthe -gasoline boiling range and has as its primary purpose theimprovement of the antlknock characteristics of the material treated.Another and related object is to eect a general or a partial lowering ofthe boiling range. Still another object is to reduce the sulphur contentof the material treated. Still another object 1o is to produce the aboveresults with a minimum of loss.

To meet the requirements of automotive 'engines and the specificationsfor motor fuels suitable therefor reiiners have resorted to variousexpedients to improve the antiknock ratings of their products. Oneexpedient is to mix with the iinished product a chemical substance whichmodifies the rate of combustion of the fuel so as to suppress to someextent detonating edect of the fuel,

80 one such substance being tetraethyl lead, known under such names asethyl spirit or Q fluid. Such substances, being highb poisonous, aredangerous to handle and expensive to manufacture. Moreover the number ofoctane points rise which can 2s be effected by the addition of suchsubstances varies widely with the composition of the motor fuel and insome instances is quite negligible.

Another expedient is the thermal reforming of knocking hydrocarbons bythe use of heat and so pressure. Since the low boiling fraction ofstraight run gasoline contains the non-knocking components, refinershave found it necessary, in many instances, to reform the higher boilingor knocking part of natural gasoline `to 'secure an 35 adequate quantityof standard grade gasoline. The operation is, in most instances,conducted at a cracking temperature, namely, above 950 F., and atprsures in excess of 400 pounds in a once through operation. Temperatureand pressure- 40 conditions are set to produce a predetermined gas make,inasmuch as the gas make in this operation is directly related to theoctane rating of the product. The gas make is high and normally variesfrom 15% up to 30 or even 35%, depend- 45 ing upon the nature of thestock and the octane rating desired. Hence the thermal operation ofreforming is costly by reason of the heavy losses.

Many attempts have been made in 'recent years t-o effect reforming bycatalysis and there are disso closures in patents of I. G.Farbenindustrie Aktiengesellschaft and others specifying a. wide'rangeof catalysts and of operating conditions including temperatureranges from 572 to 1500 F., pressures from subatmospheric to in excessof 55 200 atmosphereafeed rates of 1:2 (one volume of oil per hour totwo volumes of catalyst) to 3:1 per hour. The U. S. patent to M. W.Boyer, No. 1,934,031, issued November 7, 1933, specifies temperaturesabove 900, 950 or 1000 F., pressures above atmospheres and preferablyabove 200 5 Vatmospheres, a feed rate of 2:1, and operation continuouslywith added hydrogen. So far as I am aware. none of the proposedcatalytic reforming processes has gone into commercial use or has beenfound to be capable of successful competi- 1o tion with thermalreforming or with octane increase by the `addition of chemicals.

During the development of various processes for the conversion ortreatment of petroleum with the aid of contact masses I have made manyat- 15 tempts to effect catalytic reforming of heavy naphtha withindifferent success. After an exhaustive and detailed study extendingover a long period, with thousands of experiments, I have finallydiscovered that heavy naphtha can be re- 20 formed by a new method ofprocedure with remarkably favorable results, especially when theoperation is effected catalytically.

|l'he drawing shows a flow sheet of the process of this application.`

The first step in the new procedure is to divide the naphtha byfractionation or otherwise into two parts, the first part covering theboiling range f of about 250 to 375 F. and the second part from about375 F. to the end point of the naphtha. 30

v'I'hese two parts are then reformed separately as follows: Each partundergoes the chosen reforming `operation and from the product isseparated the reformed material of the desired antiknock value. su'ch as75 octane, leaving a low octane 35 residue. I'his residue is thenreformed and the 7 5 octane material again removed, the procedurecontinuing until all the material of each part is brought to the desiredoctane rating. While thermal reforming may be used with a certain meas-40 ure of success, I prefer to use a catalytic reforming operation,since it gives a larger percentage of easily separated material of thedesired octane rating, but the operating conditions are critical anddivergence from any of them beyond a relatively narrow range issufficient to upset yield, or product, or both.

The results of the initial fractionation of the charge combined withseparate catalytic reforming of the fractions are most surprising andunexpected. In the first place, liquid yield as high as v100% isattainable. In the second place, the octane rating off' the convertedproduct is above 70 and usually about 75 (C.F. R. Motor Method)regardless of the charging material. In the third place, the gas makehas little or no eifect upon the antiknock improvement of the charge.

Factors in the most successful operation of my process comprise,catalyst, temperature, pressure, feed rate or time of contract ofreactants, length of period on-stream (which takes into account thechanged characteristics-of the catalyst due to deposit of contaminantsas the reaction period progresses), and added gaseous material, inaddition to the particular nature of the hydrocarbon charge. Preferredconditions of temperature.

and/or pressure vary, for example, as the feed rate or activity ofthecatalyst varies. By way of illustration as the time of contact ofreactants with the catalyst is increased, the temperature and/orpressure may be reduced somewhat, and vice versa. Illustrative relativeconditions of operation appear hereinafter.

Salient features' of the present invention, involve: (1) maintaining thefraction of reactants charged to a reforming zone within a relatively orfairly narrow boiling range, e. g; dividing the raw naphtha charge intofractions, one boiling below substantially 375 F. and another boilingabove substantially 375 F. or dividing the naphtha charge into fractionseach having a boiling range of approximately 100 F. and (2) controllingthe rate of feeding the naphtha fraction to the catalyst as hereindefined and illustrated.

Reforming in a series of separate passes, is, inter alia,` also animportant feature of this invention.

The charge most particularly contemplated is a naphtha predominately inthe boiling range of 250 to 450 F. which is divided into two or morefractions, e. g., 250 to 375 F. and 375 F. to end point respectively.These parts must be reformed separately. Several passes are usuallyrequired for best results.

The catalyst is essentially a blend of silica and alumina with as littleextraneous material as possible. The weight ratio of silica and aluminashould be not less than three to one, preferably four to one, orsomewhat higher. The catalyst may be formed in various ways, as forexample, precipitating silica on alumina, or alumina on silica, o r bycombining a silica gel with alumina. Another way is to take a naturalcompound, such as a clay in the form of fullers earth, kieselguhr,bentonite, china clay, or the like, and then leach it with acids ortreat it with other substances such as phosgene and various alkalies.The resulting product is used as a base or carrier on which to buildback the desired silica to alumina ratio. In some instances, improvedresults are'secured by incorporating in the catalyst a small quantity ofthe oxide of one or more of the following metals-iron, lead, copper,manganese, vanadium, molybdenum, chromium, tungsten. The catalyst isformed in bits,

broken fragments, or molded pieces of substantially uniform size so asto be capable of regeneration in place.

The temperature must be between 850 and 925 F. and preferably between875 and 925 F.

The pressure may vary between 15 and 300 pounds per square inch gauge.An excellent op eration is secured at 75 pounds. One advantage obtainedby raising the pressure up to 300 pounds is an improvement in the rateof feed.

The feed rate may vary from 3:5 (three volumes of oil per hour to fivevolumes of catalyst) to.7 :5. A good rate for seventy-'five poundspressure is 1:1. y

The period of operation varies from one-half to two hours, and comprisesthe time necessary to feed to the catalyst a quantity of oil varyingfrom one-fourth the volume to a volume equal to twice that of thecatalyst. The run generally averages from forty-five minutes to one andonehalf hours, the catalyst being thereafter regenerated to remove cokeand tarry deposits in preparation for another run.

Extraneous gaseous material, in the form of steam or refractory gasessuch as vmethane. ethane, propane, butane, hydrogen or mixtures of thesame, is added to the extent of from 2 to 5% by weight of the charge forthe purpose of inhibiting secondary reactions and to reduce the depositof contaminants upon the catalyst.

The operation is conducted so as to produce only a small amount of gas.as of the order of 4 to 7% per pass. This is enough to insure a goodreaction and nothing is gained by making more gas. `The products of thereaction are topped by fractionation to separate out the lower boilingconverted material of increased octane rating, as above 70. Normallyabout 50% of the charge is converted into high octane material. Theremainder, which usually shows some slight improvement in octane overthe charge, may be subjected, with or without fresh charge, to a secondconverting operation, and the procedure continued until all `thematerial is converted.

Since the charge is changed into lower gravity material, and since thegas make and the carbon deposit are low, the yield in liquid is veryclose to 100%.

First example The 65% or light cut was fed to a catalytic mass of theabove described type maintained' at a temperature of 875 F., at acharging rate of 1:1, under 75 pounds pressure, with 2% of steam, forone hour.- The gas make was 4.3% by weight and the coke deposit on thecatalyst 1.5%, the resulting products being topped to secure a 39%overhead having an octane rating of 72.7. The recycle material was sentin a second pass into the conversion zone under the same operatingconditions., except that the reaction temperature was raised to 900 F.The gas make was 5% by weight and the coke deposit on the catalyst 1.8%,and a high octane overhead cut comprising 42% of the products wasseparated out having an octane rating of 70.7. The bottoms or recyclematerial from the second pass was sent for a third pass under the sameoperating conditions as for the second pass, except that the chargingrate was reduced to 4:5. The gas make was 5.5% by weight and the cokedeposit on the catalyst 3.3%, and the products were topped to obtain a%'yield of 73.7 octane gasoline. The overall yield for the three passeswas 73% of gasoline with an octane rating of 72 (C. F. R.. MotorMethod). There was approximately 20% of recyclematerial remaining havingan A. P. I. gravity of 40, a boiling range of 315 to 470, and

an octane rating of 50.

The 35% bottoms of the East Texas naphtha were catalytically convertedseparately as fcl-` lows: The first pass was made at a charging rate of3:5 with 5% steam to catalyst of the above described type. under 65pounds pressure at a temperature of 882 F. for 45 minutes. The gasmake'was'7% and the coke deposit 1%, and 48% `oi' 80 (C. F. R.Motor'Method) The ilnal yieldv for the three passes from the 35%,.bottomcut l of East. Texas naphtha was 83% of 80 octane gasoline and 13% oi'recycle material of 50 octane v rating.`

The total average yield from the reforming operation on both cuts of theoriginal heavy naphtha was 76.3% of gasoline of 76 octane rating (C. F.R. Motor Method). The bottoms left, suitable'for recycling, comprised17.5% of the original charge with a 50 octane rating.

Second example A California naplitha of 40.5 A. P. I. gravity, with aboiling range of 300 to 495 and an octane rating of 32, was divided intoa light cut of approximately 35%, having a gravity of 46.8, and

-a boiling range of 300 to 375, with an octane minutes, producing 4.5%of gas and 1% coke and yielding 40% of 76 octane gasoline. The

bottoms from-the ilrst pass were subjected to a second pass under thesame conditions, except that the feed rate was 4:5 and produced 4.4% gasand 1% coke, with a yield of 39.6% gasoline of 76 octane. 'Ihe bottomsfrom the second pass were subjected to a third pass under the sameoperating conditions as the first pass, except that the temperature wasraised to 900 F. I'he gas make was 5% and the coke deposit 1.2%, theyield being 38.2% of 76 octane rating. The total yield for the light cutwas 76% of 76 octane gasoline (C. F. R.. Motor Method) and about 20% ofrecycle material having an octane rating of 50.

For lthe heavy cut of California naphtha,- the first pass was made onthe catalyst at 875 F. at a charging rate of 4:5 under 55 poundspressure with 5% of steam for 45 minutes. 6% of gas was produced andthere was a coke deposit of 2% on the catalyst. The products weresubjected to fractionation, obtaining an overhead cut of'40% gasoline of80- octane rating. The bottoms vsfrom. the rst pass were subjected to asecond-pass under the same conditions producing 6.2% gas, a coke depositof 1.8% and yielding 41% of 80 octane gasoline. The third pass was madeat' 900' F., the other conditions being the same and the gas make was6.1%, the coke deposit 2.1% and the yield of 80 octane gasoline was38.7%. 'I'he total yield for the heavy cut was 75% of 80 octane gasoline(C. F. R. Motor Method) and 18% of recycle material of 50 octane.

When the products from both cuts were blended, the total yield for-theCaifornia naph` tha reformed was 75.35% of 78 octane gasoline and 18.7%of heavy material suitable for further recycling of 50 octane rating.

` Third example original material, was subjected to four passes.

The rst pass was sent to a catalyst of the above described typemaintained at 875 F. at a charging rate of 7:10 with 2% of steam under75 pounds pressurefor 60 minutes. The gas make was 7%, the` coke depositon the catalyst 1.5%, and the products, when topped, yielded 25% ofgasoline of 72 octane rating (C. F. R. Motor Method). 'Ihe second passwas at the rate of 4:5, with the catalyst at 900 F., the otherconditions being the same, producing 6.8% of gas, a coke deposit of1.4%, and yielding-23.2% of 72 octane gasoline. The third pass was nadeat 4 the rate of 7:10 under conditions otherwise the same as in thesecond pass, producing 7.2% of gas, a coke deposit of 1.6%, and yielding24.5% of 72 octane gasoline. The fourth pass was made under the sameconditions as the third, with a gas make of 6.8%, a coke deposit of1.6%, and yielding 23.5% of 72 octane gasoline. The nal yields for thefour passes of the light cut were 61% of 72 octane gasoline (C. F. R.Motor Method) and 24% of bottoms or recycle material of 0 octane rating.

'I'he heavy Michigan cut, comprising 35% of the original material, wassubjected to three passes. The first pass was made on catalyst of theabove described type at 875 F. at a charging rate of 4:5 with 5% steamat 55 pounds pressure for 4,5,.minutes. I'he gas make was 7.5, the cokedeposit 2%, and the yield was 32% of 72 octane 4gasoline (C. F. R. MotorMethod). The secondV pass was made on the catalyst at 900 F., at acharging rate of 7:10, with 5% steam and under` 65 poundsV pressure,producing a gas make of 7.8%, a coke deposit of 2.8% and yielding 28.5%of 74 octane gasoline. The third pass was made under the same conditionsas the second pass with a gas make of 7.7%, a coke deposit of 2.9%,andthe yield was 28% of 74 octane gasoline. The total yield of the threepasses of the heavy cut was 61.5% of 73 octane gasoline (C. F. R. MotorMethod) and the bottoms or recycle material of -0 octane which remainedwas 29.5%.

The products of both the heavy and the light cuts, after reforming, whenblended, gave 61.2% of 72 octane gasoline and 25.9% of bottoms suitablefor further recycling of -0 octane rating.

The gas produced from all operations in accordance with the presentinvention is of high quality. Itfhas a high specic gravity (1.3 to 1.5)and a high olenic content. By removing from the gas all oftheconstituents which are in the gasoline boiling range. such as butaneand heavier, a considerable quantity of gasoline of a very high octanerating, over 90 (C. F. R. MctmA Method) can be recovered which issuitable for blending with the reformed naphtha or with other gasoline.Also, the oleflns contained in the gas can be polymerized to produce afurther yield of gasoline of high octane number. By these means, thetotal yield of high octane gasoline can be raised, in some cases, asmuch as 8 to 10%, and the octane number by two points.

In order to determine where to cut the product to separate out thetransformed material of the desired octane rating, it is customary tomake an experimental run on laboratory apparatus with the charging stockunder suitable predetermined conditions. It is then found, for example,that a overhead fraction gives an 80 octane, that a deeper cut such as46% gives 77 octane,

and that a still deeper cut such as 56% will give a 73 octane. 'I'hus itis possible to'cut for a definite octane value of the reformedymaterial, or to obtain a denite yield, as taking the octane improvementwhich such a yield offers.

I claim as my invention:

` 1. In the reforming of a naphtha charge to improve its antiknockcharacteristics, the process which comprises dividing the charge into aplurality of fractions of dierent boiling range characteristics, eachhaving a boiling range of not more than 125 F., subjecting each of saidfractions to a separate reforming operation, each of said operationsinvolving treating the respective naphtha fraction in a'plurality ofseparate reaction steps, the low boiling portions of the products fromeach reaction step which have an octane rating above approximately 70 C.F.- R. M. M. being separated from the remaining higher boiling orbottoms fraction before the latter is subjected to the next succeedingreaction step, each of said steps being effected in a reaction zonecontaining a catalyst comprising'a blend of silica and alumina and beingmaintained under a superatmospheric pressure not greater thanapproximately 300 lbs/sq. in. gauge, and at a temperature within therange of 850 to 925 F., and blending the products of each of thereforming steps having an `octane rating above approxi'- mately 70 C. F.R. M. M. to provide a high yield of high quality product from saidnaphtha charge and a low concomitant `production of coke and fixed gas.

2. In the reforming of a naphtha charge to improve its antiknockcharacteristics, the process which comprises dividing the charge into aplurality of fractions of different boiling range characteristics, apredominant proportion of each boiling within a range of not more than100 F., subjecting each fraction separately, in at least one confinedreaction zone, to the action of an adsorptive contact mass containedtherein, said mass comprising a blend of silica and alumina with thepermissible addition of other active material and being maintained at asuperatmospheric pressure not greater than approximately 300 lbs./sq. ingauge and at a temperature approximately within the range of 850 to 925F., and blending together at least a portion of the products from thesaid reaction zones having an octane rating above a predeterminedsatisfactory minimum so as to effect the desired improvement inanti-knock characteristics of low boiling components as well as of highboiling components of the aforesaid charge while keeping the concomitantproduction of coke and fixed gases at a low amount in proportion to theamount of said charge. i

3. In the reforming of a naphtha charge boiling substantiallycompletelybelow approximately 450 F. to improve its antiknock characteristics,

the process which comprises dividing the naph charge into at least twofractions of different boiling range characteristics, a first fractionboiling predominantly above 375' 1 and a second fraction boilingpredominantly below 375 1'. and subjecting each fraction to a separateplurality of reforming steps in separate reaction zones held atprogressively increasing temperatures, the lower boiling fractionjof theproducts from each. of

` said reaction zones having an octane rating above a predeterminedminimum being separated from the remaining or bottoms fraction lbeforethe latter is subjected to the next succeeding reaction step, each stepbeing effected in a reaction zone containing an adsorptive contactmasscomprising a blend of silica. and'alumina and being main- 4tainedunder a superatmospheric pressure not greater than approximately 300lha/sq. in. gauge and at a temperature substantially within the range of850v to 925 F.

` 4. In the reforming of a naphtha charge boiling substantiallycompletely below approximately 450 F. to improve its antiknockcharacteristics,

the range of 850 to 925 F. and under superatmospheric pressure, andblending together portions of the products of the higher and lowerboiling fractions of said charge which have an octane rating above apredetermined satisfactory minimum so as to arrive at a high yield ofhigh quality product while keeping the concomitant production of cokeand fixed gases at a low amount in proportion to the amount of theaforesaid charge.

5. In the reforming of a naphtha fraction to improve its anti-knockcharacteristics, the process which comprises subjecting the naphtha instraight passes to a first reforming step at a temperature of about 875F., fractlonating the products of the f'lrst reforming step so as toobtain an overhead fraction of at least 70 octane rating C. F. R. M. M.and a first bottoms fraction, subjecting said first bottoms fraction toa second separate reforming step at a temperature of about 900 F.,fractionating the products of said second reforming step so asY toobtain an overhead fraction of at least 70 octane rating C. F. R. M. M.

land a second bottoms fraction, passing said second bottoms fraction toa third reforming step wherein it is subjected to a temperature of about925 F.l and separating the products of said third reforming step into anoverhead fraction of at least 70 octane rating C. F. R. M. M. and alower octane bottoms fraction, each of said reforming steps beingconducted under a suitable superatmospheric pressure of the order ofapproximately 75 lbs./sq. in. gauge and in the presence'of catalyticmasses, eachl comprising essentially blends of silica and alumina havinga weight ratio of silica to alumina of at least approximately 4 to l.

6. In the reforming of a naphtha charge boiling substantially completelybelow approximately 450 F. to improvepits antiknock characteristics, theprocess whichcomprises dividing the naphtha charge into at least twofractions of Vdifferent boiling range characteristics, a first fractionboiling predominantly above 375 F. and a second fraction boilingpredominantly below 375 F., subjecting said first fraction in successivepasses to a rst reforming step at ay temperature of about 875 F.,fractionating the products of the first reforming step so as to obtainan overhead fraction of at least 70 octane rating C. F.'R. M. M. and afirst bottoms fraction,y subjecting said rst bottoms fraction to asecond separate reforming operation at a temperature of about 900 F.,fractionating the products of the second reforming step or operation soas to obtain an overhead fraction of at least 70 octane rating C. F. R.M. M. and a second bottoms fraction, passing said second bottomsfraction to a third reforming step wherein it is subjected to atemperature of about i925 F.

and separating the products of said third reforming step into anoverhead fraction of at least 70 octane rating C. F. R. M. M. and Yalowe octane bottoms fraction, and subjecting the aforesaid secondfraction to at least one separate reforming step, each of said reformingsteps being conducted under the suitable superatmospheric pressure ofthe order of approximately '75 lbs ./sq. in. gauge and in the presenceof catalytic masses, each comprising essentially blends of silicay andalumina having weight ratio of silica to alumina of at leastapproximately 4 to 1.

EUGENE J. HODRY.

